The present invention concerns a vacuum drainage system for sanitary equipment such as toilets, urinals and sinks etc., comprising branching pipes which are connected to the sanitary equipment and which open into a collecting pipe, as well as a vacuum device connected to the collecting pipe to achieve a vacuum in the pipes and transport of waste from the sanitary equipment to a collecting tank, a purifying plant, a drainage device etc.
Waste treatment devices of the above mentioned type are today dominating in connection with use aboard ships, planes and trains. However, on land such plants are also increasingly used, and the background for this is primarily the reduced use of water and the flexible system for the pipes given by such systems.
From Swedish publication no. 389.882 there is previously known a vacuum drainage system where a circulation pump is mounted in a pipe loop and is equipped to stir, divide and aerate the contents in the tank. An ejector pump is further connected to the pipe loop and produces a vacuum in the drainage system. The ejector pump is thus driven by the sewer which is circulated in the pipe loop by the circulation pump. It is, however, a major drawback with the circulation pump, which is of a centrifugal type, that it easily is clogged by textiles, sanitation utensils etc. which enters the tank. By such a clogging the pump must be removed and cleaned, something which means a break in its operation and increased operation costs. In addition it is a major disadvantage with such drainage systems that they comprise a large and space-requiring collecting tank which makes it unsuited for use in facilities, inter alia smaller boats, where the room is scarce.
The system is otherwise expensive to produce/build since it uses two pumps, an ejector pump and a centrifugal pump together with an extra pipe loop and collection tank.
The tank must have such a size and at every time be able to contain such a fluid quantity (sewer) that foaming in the tank is avoided. Foaming of the fluid results in the ejector losing its pumping effect, and it has been shown in practice that even if there is maintained a large circulating fluid quantity in the tank will foaming arise anyway in some cases, inter alia in connection with cleaning of-the toilets where soap water is supplied to the tank.
In the applicant's own Norwegian patent application no. 87.1539 there is shown a collection system for vacuum drainage systems wherein it is used a vacuum tank with two chambers an a separately driven grinder. Sewer is supplied to the first chamber of the tank and is ground and transferred to the second chamber by using the grinder. A vacuum pump, inter alia a screw pump, produces vacuum in the tank and pumps the contents of the said second chamber out of the tank. Even if one with the above mentioned system has solved the problems with clogging and operation halt, the system is comparatively expensive to build and relatively space-requiring.